Half-mast, or half-staff, describes the act of flying a flag approximately halfway up a flagpole (though anywhere from one-third to two-thirds of the way up the flagpole is acceptable). This is done in many countries as a symbol of respect, mourning, or distress.

When hoisting a flag that is to be displayed at half-staff, it should be hoisted to full staff for an instant, then lowered to half-staff. Likewise when it is lowered at the end of the day, it is to be hoisted to full staff for an instant, and then lowered.

The original flag 'etiquette' was to fly the flag at one flags depth from the top of the hoist. With the larger flags on shorter hoists on public buildings the practice of 'half-mast' has now commonly become to fly the flag at true 'half-mast' regardless of the size of the flag or hoist.

Flags are flown at half-mast in Canada:

• Upon the death of the Sovereign, the current Governor General of Canada or the current Prime Minister of Canada: from the time of notification of death until sunset on the day of the funeral or the memorial service.
• Upon the death of the Sovereign's spouse, the Heir to the Throne, the Heir of the Heir to the Throne, a former Governor General, the Chief Justice of Canada, government ministers, or a former Prime Minister: from the time of notification of death until sunset on the day of the funeral or, if there is to be a memorial service, the half-masting should take place from the time of notification of death until sunset the following day and from sunrise to sunset on the day of the memorial service.
• April 28, Day of Mourning for Persons Killed or Injured in the Workplace (coinciding with World Day for Safety and Health at Work)
• Last sunday in September, Police and Peace Officers' National Memorial Day
• November 11, Remembrance Day
• December 6, National Day of Remembrance and Action on Violence Against Women.
• Many discretionary provisions apply, and some occasions exist where the flag is half-masted at the Peace Tower but not at other federal facilities. (one example is America Remembers)
  • Sometimes, at discretionary occasions, the flag is half-masted not just at the Peace Tower, but on all other federal facilities (some examples included 9/11, 9/11 anniversary, state funeral of Ronald Reagan, the tsunami, the RCMP massacre in Mayerthorpe, Ab., death of Pope John Paul II, 20th anniversary of Air India Flight 182, London bombings), and following the death of Ernest Alvia "Smokey" Smith (the last living Canadian recipient of the Victoria Cross).

The flag is flown at half-mast for the death of the President, Vice-President and Prime Minister all over India. For the Speaker of the Lok Sabha and the Chief Justice of The Supreme Court of India, it is flown in Delhi and for a Union Cabinet Minister it is flown in Delhi and the state capitals. For Minister of State, it is flown only in Delhi. For a Governor, Lt. Governor and Chief Minister of a state or union territory it is flown in the concerned state.

If the intimation of the death of any dignitary is received in the afternoon, the flag shall be flown at half-mast on the following day also at the place or places indicated above, provided the funeral has not taken place before sun-rise on that day. On the day of the funeral of a dignitary mentioned above, the flag shall be flown at half-mast at the place of the funeral.

In the event of a half-mast day coinciding with the Republic Day, Independence Day, Mahatma Gandhi's birthday, National Week (6th to 13th April), any other particular day of national rejoicing as may be specified by the Government of India or in the case of a state, on the anniversary of formation of that state, flags are not permitted to be flown at half-mast except over the building where the body of the deceased is lying until such time it has been removed and that flag shall be raised to the full-mast position after the body has been removed.

Observances of State mourning on the death of foreign dignitaries are governed by special instructions issued from the Ministry of Home Affairs (Home Ministry) in individual cases. However, in the event of death of either the Head of the State or Head of the Government of a foreign country, the Indian Mission accredited to that country may fly the national flag on the above mentioned days.

Flags are flown at half-mast in Israel:

• On Yom HaShoah, or the Holocaust Remembrence Day.

There was some controversy in the United Kingdom in 1997 following the death of Diana, Princess of Wales that no flag was flying (at half mast or otherwise) at Buckingham Palace. Until 1997, the only flag to fly from Buckingham Palace was the Royal Standard, the official flag of the reigning British sovereign, which would only fly when the sovereign was in residence at the Palace (or, exceptionally, after the death of the sovereign, the flag of the next senior member of the Royal Family would be raised); otherwise, no flag would fly, and a flag would never fly at half mast, even in times of mourning.

In response to public outcry that the palace was not flying a flag at half mast, the Queen ordered a break with protocol and the Union Flag was flown at half mast over the Palace on the day of Diana's funeral. Since then, the Union Flag flies from the Palace when the Queen is not in residence, and has flown at half mast upon the deaths of members of the Royal Family, such as the Queen Mother and Princess Margaret, and other times of national mourning such as following the terrorist bombings in London on 7 July 2005.

In the United States, the President can issue an Executive Order for flags to be flown at half-staff. When such an order is issued, government buildings, offices, and military bases are to fly their flags at half-staff. Private organizations and individuals usually also fly their flags at half-staff at these times, but are not required by law to do so.

• For thirty days after the death of a current or former President.
• For ten days after the death of a current or former Vice-President, Chief Justice, or Speaker of the House of Representatives.
• From the day of death until interment of an Associate Justice of the Supreme Court, a Secretary of an executive or military department, a former Vice President, or the Governor of a State, territory, or possession
• On the day of death and the following day for a Member of Congress
• Until 12:00pm on Memorial Day
• On Executive Order by the President or State Governor (some examples include for remembrence of the 9/11 attacks, the death of Pope John Paul II, and the Indian Ocean tsunami).
• By Presidential proclamation on December 7, "National Pearl Harbor Remembrance Day," as required by Federal law.

• Flag of Hong Kong#Half mast

• US Flag Code Concerning Flag Display
• Canadian Heritage announcements of half-masting
• Canadian rules for half-masting